WPF create class library

For example, see the image below:

This picture is a test project for beginners, and it has no effect. Main recording method:

1. First create the project EFDemo;

slightly.

2. Add a new project under the solution, select the class library, and name it (I am here for testing, the default ClassLibrary1);

3. Add the newly created ClassLibrary1 class library to the reference of the EFDemo project, and then add the namespace where the library class needs to be used in the project: using ClassLibrary1;

Note: The new class in the class library needs to add public permission, otherwise an error will be reported.